In many systems and devices, audio signals are used to attract the attention of a human user. Such audio signals may be safety critical and it may be important to ensure that the audio signals are heard and/or acknowledged by the user. In some systems, safety critical audio signals are played at a loud volume and/or are played repeatedly to increase the probability that they are heard. It may also be important to ensure that audio signals are played correctly, i.e. that the user hears an intended and correctly reproduced signal or message in order to be able to interpret it in the way the system expected.
US 2010/161089 A1 discloses a sound message generating device with integrated defect detection. The detection principle used therein consists in digitally superposing, onto the input of a digital-analogue converter receiving the samples of the audio sequences to be restored, a digital test signal having a spectrum of frequencies outside of the spectrum of frequencies of the audio sequences of the data bank, and in extracting a corresponding test signal, the characteristics of which are compared with those of the test signal applied as input.
A safety system in a vehicle may be designed to ask the driver of the vehicle, via an audio signal or message, to perform a safety routine to ensure that the driver is present and is able to continue driving the vehicle. As a safety mechanism, the vehicle may be adapted to stop automatically unless the driver performs the requested safety routine within a given time period. Automatic stops caused by the driver misinterpreting or not even hearing the audio signal may be frequent in systems with poorly functioning audio processing devices, and so, it is important to ensure that the audio signal is played correctly.
At least for the above described reasons, it would be desirable to provide an audio processing system enabling more reliable (or safer) playback of audio signals and/or audio messages.